For a high speed serial link transceiver, signal integrity and power are two major concerns. Signal integrity can be affected by channel characteristics (i.e.,skin loss, dielectric loss and return loss). Channel characteristics can change over time due to operating environment changes. Operating environment changes can include changes in temperature, humidity, and power supply voltage. Adapting equalizer parameters during initialization and freezing equalizer parameters thereafter ignores operating environment changes. Ignoring operating environment changes can result in performance degradation. Power consumption is a concern because over two hundred serial link transceivers can be integrated on one chip today.
Users of serial link transceivers typically focus on getting error-free data transmission and do not consider power consumption. To achieve a low bit-error ratio (BER) in long-reach channels at high transmission speed, equalization methods such as linear equalization (LE) and decision feedback equalization (DFE) are used to overcome channel loss. Optimal, or close to optimal, performance depends on properly setting equalizer parameters, such as tap coefficients, gain factor and filter pole/zero positions. Conventional adaptation bandwidth control is manual. Manual adaptation bandwidth control makes the serial link transceivers difficult to use in the field. Adapting equalizer parameters too frequently (high bandwidth) adds jitter due to parameter quantization noise. Adapting equalizer parameters too infrequently (low bandwidth) can smooth out excessive changes in the parameters, but may miss operational environment changes.
It would be desirable to have an automatic adaptation bandwidth control and scheduling of equalizer parameter updates.